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Description and Validation of the Texas A&M Sheep Simulation Model¹

Texas Agricultural Experiment Station, College Station 77843

Abstract

A computer simulation model was developed to simulate individual sheep and accumulate them into flocks. The model was constructed to allow investigations of the effects of varying genetic potentials, nutritional levels and management alternatives on estrus, conception, birth, lactation, nutrient intake, growth, wool growth and death of sheep. Both protein and energy requirements were simulated in the model. Utilization of protein and energy were accounted for in terms of body weight change (lean and fat) and maintenance. Model validation was conducted using data collected over 2 yr in arid northern Kenya, which included monthly estimates of diet quality, mature ewe body weight, lamb growth to 300 d of age, daily milk production and ewe reproduction. For validation, a flock of 300 breeding ewes was simulated for 10 yr. The flock reached steady-state, with reference to number of breeding ewes, at the fifth year; data from the last 3 yr were averaged and compared with actual data. Comparison of actual and simulated data indicated that the model did simulate the response of sheep in the northern Kenya production setting. Although differences in magnitude and direction occurred at specific points in time, these were not large and tended not to last for more than 1 mo.

¹ Actual data were collected by Dr. C. R. Field of the Integrated Project on Arid Lands, part of UNESCO's Man and the Biosphere Program. Model development and analysis were supported in part by funds from the United States Agency for International Development Title XII Small Ruminants Collaborative Research Support Program under grant No. AID/DSAN/XII-G-0049 in collaboration with the Kenya Ministry of Agriculture and Livestock Development.

² Anim. Sci. Dept.

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